/*
FUNCTION
<<qsort>>---sort an array

INDEX
    qsort

ANSI_SYNOPSIS
    #include <stdlib.h>
    void qsort(void *<[base]>, size_t <[nmemb]>, size_t <[size]>,
           int (*<[compar]>)(const void *, const void *) );

TRAD_SYNOPSIS
    #include <stdlib.h>
    qsort(<[base]>, <[nmemb]>, <[size]>, <[compar]> )
    char *<[base]>;
    size_t <[nmemb]>;
    size_t <[size]>;
    int (*<[compar]>)();

DESCRIPTION
<<qsort>> sorts an array (beginning at <[base]>) of <[nmemb]> objects.
<[size]> describes the size of each element of the array.

You must supply a pointer to a comparison function, using the argument
shown as <[compar]>.  (This permits sorting objects of unknown
properties.)  Define the comparison function to accept two arguments,
each a pointer to an element of the array starting at <[base]>.  The
result of <<(*<[compar]>)>> must be negative if the first argument is
less than the second, zero if the two arguments match, and positive if
the first argument is greater than the second (where ``less than'' and
``greater than'' refer to whatever arbitrary ordering is appropriate).

The array is sorted in place; that is, when <<qsort>> returns, the
array elements beginning at <[base]> have been reordered.

RETURNS
<<qsort>> does not return a result.

PORTABILITY
<<qsort>> is required by ANSI (without specifying the sorting algorithm).
*/

/*-
 * Copyright (c) 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdlib.h>

#ifndef __GNUC__
#define inline
#endif

static inline char  *med3(char *, char *, char *, int (*)(const void*, const void*));
static inline void   swapfunc(char *, char *, int, int);

#define min(a, b)   (a) < (b) ? a : b

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) {       \
    long i = (n) / sizeof (TYPE);           \
    register TYPE *pi = (TYPE *) (parmi);       \
    register TYPE *pj = (TYPE *) (parmj);       \
    do {                        \
        register TYPE   t = *pi;        \
        *pi++ = *pj;                \
        *pj++ = t;              \
        } while (--i > 0);              \
}

#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
    es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;

static inline void swapfunc(char *a, char *b, int n, int swaptype)
{
    if(swaptype <= 1) 
        swapcode(long, a, b, n)
    else
        swapcode(char, a, b, n)
}

#define swap(a, b)                  \
    if (swaptype == 0) {                \
        long t = *(long *)(a);          \
        *(long *)(a) = *(long *)(b);        \
        *(long *)(b) = t;           \
    } else                      \
        swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n)    if ((n) > 0) swapfunc(a, b, n, swaptype)

static inline char * med3(char *a, char *b, char *c,
        int (*cmp)(const void *, const void *))
{
    return cmp(a, b) < 0 ?
           (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
              :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
}

void qsort( void *a, size_t n, size_t es,
        int (*cmp)(const void *, const void *))
{
    char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
    int d, r, swaptype, swap_cnt;

loop:   SWAPINIT(a, es);
    swap_cnt = 0;
    if (n < 7) {
        for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
            for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                 pl -= es)
                swap(pl, pl - es);
        return;
    }
    pm = (char *) a + (n / 2) * es;
    if (n > 7) {
        pl = a;
        pn = (char *) a + (n - 1) * es;
        if (n > 40) {
            d = (n / 8) * es;
            pl = med3(pl, pl + d, pl + 2 * d, cmp);
            pm = med3(pm - d, pm, pm + d, cmp);
            pn = med3(pn - 2 * d, pn - d, pn, cmp);
        }
        pm = med3(pl, pm, pn, cmp);
    }
    swap(a, pm);
    pa = pb = (char *) a + es;

    pc = pd = (char *) a + (n - 1) * es;
    for (;;) {
        while (pb <= pc && (r = cmp(pb, a)) <= 0) {
            if (r == 0) {
                swap_cnt = 1;
                swap(pa, pb);
                pa += es;
            }
            pb += es;
        }
        while (pb <= pc && (r = cmp(pc, a)) >= 0) {
            if (r == 0) {
                swap_cnt = 1;
                swap(pc, pd);
                pd -= es;
            }
            pc -= es;
        }
        if (pb > pc)
            break;
        swap(pb, pc);
        swap_cnt = 1;
        pb += es;
        pc -= es;
    }
    if (swap_cnt == 0) {  /* Switch to insertion sort */
        for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
            for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; 
                 pl -= es)
                swap(pl, pl - es);
        return;
    }

    pn = (char *) a + n * es;
    r = min(pa - (char *)a, pb - pa);
    vecswap(a, pb - r, r);
    r = min(pd - pc, pn - pd - es);
    vecswap(pb, pn - r, r);
    if ((r = pb - pa) > es)
        qsort(a, r / es, es, cmp);
    if ((r = pd - pc) > es) { 
        /* Iterate rather than recurse to save stack space */
        a = pn - r;
        n = r / es;
        goto loop;
    }
/*      qsort(pn - r, r / es, es, cmp);*/
}

